At least 33 civilians have been killed and scores of others have been injured in a government airstrike on a market in the rebel-held Syrian city of Aleppo, according to the Syrian Observatory for Human Rights.

The UK-based anti-government monitoring group held that regime war planes struck a market in the opposition-held Halak district in Aleppo.

"A Syrian fighter jet fired a missile at the [Halak] neighbourhood, and within minutes it fired another," Rami Abdel Rahman, the head of the Observatory, said.

The Aleppo Media Centre estimated the death toll to be as high as 44.

Local activists who run the centre said "two residential buildings were destroyed and several shops set ablaze".

The attack came one day after a Syrian regime air raid struck a school and killed at least 19 people, including at least 10 children, in the same city. That air raid was described by the UN's humanitarian chief as "a flagrant violation of the basic tenets of war".

Aleppo has been divided between government forces and opposition fighters for almost two years and has been repeatedly struck by forces loyal to Syria’s President, Bashar al- Assad.

More than 150,000 people have died and millions of others have been displaced in three years of conflict.